Many attempts have been made to simulate natural daylight by artificial means. Some of the more successful devices for this purpose are described in applicant's U.S. Pat. Nos. 5,079,683, 5,083,252, and 5,282,115; the entire disclosure of each of these U.S. patents is hereby incorporated by reference into this specification.
The apparatus of U.S. Pat. No. 5,282,115 is illustrative of these prior art devices. This apparatus contains a light source and a single filter. The single filter is comprised of a color correcting filter material and a neutral density filter material. While the apparatus is adjusted, the spectral distribution of the light which passes through it varies continuously, but the brightness and/or irradiance of such light is substantially constant.
However, none of the devices of applicant's U.S. patents, and none of the prior art devices known to applicant, readily lend themselves for use in many commercial and residential settings. Thus, e.g., such prior art devices cannot readily be used in the dressing rooms of clothes stores, in jewelry stores, on the counters of cosmetic departments of department stores, in design studios, and the like.
Furthermore, none of these prior art devices known to applicant can be readily and effectively used to treat "seasonal affective disorder." This disorder, which is characterized by depression and often is also often characterized by fatigue, difficulties in concentrating, cravings for carbohydrates, and weight gain, is also often referred to as the "Winter blues." See, e.g., an article by Norman E. Rosenthal et al. entitled "Phototherapy for Seasonal Affective Disorder," Journal of Biological Rhythms, Volume 3, Number 2, 1988, pp. 101-120. Also see an article by Bosghos I. Yerevanian et al. entitled "Effects of Bright Incandescent Light on Seasonal and Nonseasonal Major Depressive Disorder," Psychiatry Research, 18, 355-364 (1986).
It is commonly agreed that "seasonal affective disorder" is caused by a deficiency of exposure to daylight. The devices used to treat this disorder, however, do not supply daylight to the patient.
Thus, for example, one such device is described in U.S. Pat. No. 4,911,166, which discloses a portable light delivery system which uses a point source of light (such as a high intensity halogen bulb) and a positive lens adapted to direct a large fraction of the light from the bulb directly into a patient's eyes. Not only is daylight not delivered by the device of this patent, but a patient must be fitted with such device in order to be treated.
It would be desirable to be able to equip an indoor environment with a lighting assembly which could provide daylight without the occupants having to actively or consciously attempt to be exposed to such daylight. Thus, it would be desirable to have a lamp assembly which could be used to provide daylight in such indoor environment.
To the best of applicant's knowledge, no such lamp assembly exists; and the prior art tends to teach that such assembly would be very difficult to produce.
Thus, e.g., U.S. Pat. No. 4,870,318 of Istvan Csanyi et al. discloses a projector lamp comprised of a light source and a mirror arranged in spaced arrangement to the light source. In referring to known light sources for emitting color light, the patentees state (at lines 10-13 of column 2) that "The afore-mentioned specifications show projector lamps equipped with a front filter and there isn't any known solution whereby projection of colour light would be possible without applying any front filter." Approximately one half of the light which is passed through such front filter generally will not be focused, and the color temperature of the output from such lamp will generally be lower than that produced when no such front filter is used.
U.S. Pat. No. 3,527,974 of Cooper describes another light source for producing a specified spectral output from an incandescent bulb. In the assembly of this patent, ". . . about 50% of the energy emitted from the lamp impinges upon the reflector thereby defining a light column having a color temperature of about 3300 K." (see lines 54-57 of column 5). The color temperature of the light spectra produced by the device of this patent is substantially lower than the color temperature of daylight, which is generally from about 4,100 to about 10,000 degrees Kelvin.
Furthermore, U.S. Pat. No. 4,839,553 teaches that, in general, "A lamp with a coated reflector, light source, and with or without a lens is limited in the range of hue and intensity to colors which are only slightly discernible from the unfiltered light of the light source" (see lines 56-59 of column 1).
Thus, none of the aforementioned patents is directed to a lamp for producing daylight. However, these patents do teach that, when one attempts to change the spectral characteristics of a bulb within a lamp, one must either use a front filter (with a concomitant loss in focus and intensity); and, even with the use of such filter, a spectral output with a relatively low color temperature will often be produced which is only slightly different from the spectral output of the bulb used in the device.
It is an object of this invention to provide a lamp with a coated reflector and light source which produces a spectral output which is substantially identical to daylight.
It is another object of this invention to provide a lamp with a coated reflector and light source which produces a spectral output with a color temperature of at least about 4,100 degrees Kelvin.
It is yet another object of this invention to provide a lamp with a coated reflector and light source which can be used with and in existing light fixtures.
It is yet another object of this invention to provide a lamp with a coated reflector and light source which is relatively inexpensive.
It is yet another object of this invention to provide a assembly which is comprised of at least one lamp with a coated reflector and light source, at least one conventional incandescent lamp, and a controller, which assembly will produce a range of spectral outputs.